Did ash fall and vegetation change by large-scale volcanic eruptions bring local extinction of small mammals?

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K03743
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 17050:Biogeosciences-related
• Research Institution: Museum of Natural and Environmental History, Shizuoka
• Principal Investigator: Nishioka Yuichiro ふじのくに地球環境史ミュージアム, 学芸課, 准教授 (00722729)
• Co-Investigator(Kenkyū-buntansha): 小林 淳 ふじのくに地球環境史ミュージアム, 学芸課, 教授 (60816461) ; 日下 宗一郎 東海大学, 人文学部, 准教授 (70721330)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: 哺乳類 / 化石 / 絶滅 / 火山噴火 / ハタネズミ / 第四紀 / 四国 / 安定同位体分析

Outline of Final Research Achievements

In order to understand the relationship between the local extinction of Japanese voles (Microtus montebelli) in Shikoku, Japan and environmental change due to the ash-fall during the Last Glacial Maximum, we carried our paleontological surveys at Saruda-do Cave (ca. 35 ka; Hidaka Village) and Anaiwa-no-ana Cave (ca. 8.8 and 7.3 ka; Sakawa Township) in Kochi Prefecture. Our field research confirmed that the cave deposits on Saruda-do Cave yield many animal remains, including voles, whereas those on Anaiwa-no-ana Cave contain a molar remain of M. montebelli with a clear layer of the Kikai-Akahoya tephra that had been fell around 7.3 ka. As a result, paleontological evidence suggests that the local population of M. montebelli had been extinct, decreasing drastically during the latest Pleistocene and the early Holocene in southern Shikoku. We also gave a preliminary result on the analysis of paleo-diet in each species of rodents which had inhabited before the catastrophic event.

Free Research Field

古脊椎動物学

Academic Significance and Societal Importance of the Research Achievements

最終氷期最寒冷期（4万から2万年前）に生息していた哺乳類（ナウマンゾウ等）がなぜ絶滅したのかについては明確な学術的証拠が得られていない現状で，本研究では，小型哺乳類が大規模な火山灰の降灰によって絶滅に至る可能性を古生物学・古環境学・火山学の複合的なアプローチによって評価した．草原性ハタネズミのように生態が特殊で個体数が著しく増減する種は，劇的で度重なる環境変化への適応力が低いことが明らかとなり，このことは現代におけるハタネズミの特性と保全に向けた基礎知識として蓄積された．